1. Field of the Invention
The present invention relates to a method of producing a molding die for use in producing (such as extruding and molding) honeycomb structure bodies made of ceramic material.
2. Description of the Related Art
A molding die for use in producing, namely, extruding and molding ceramic honeycomb structure bodies made of ceramic material has a plurality of slit grooves arranged in grid-like shape (or lattice shape). There have been proposed various related-art techniques for making such slit grooves on the molding die. In more recent years, a water jet laser slitter or cutting method is known, for example, disclosed in Japanese patent laid open publications No. JP 2002-301581 and No. JP 2003-11111.
On forming the slit grooves by a slit groove formation system equipped with a water jet laser apparatus as a laser machining apparatus, the pillar of a high-pressure water jet is supplied onto a slit groove formation position on a workpiece (as a target die plate material made of a metal plate) and the slit groove formation system irradiates a laser beam into the pillar of the high-pressure water jet. Further, the slit groove formation system equipped with the water jet laser apparatus controls so that the laser irradiation position repeatedly passes several times along the slit groove formation position in order to scan the laser beam on the workpiece
The relates-art method carries out the positioning and alignment between the slit groove formation position and the pillar formation position, onto which the pillar of a high-pressure water jet is supplied, by the following manner. At first, a reference mark is formed on the workpiece before initiating the slit groove formation. The slit groove formation system is also equipped with a camera fixed to a nozzle for jetting the pillar of a high-pressure water jet. The camera photographs the reference mark formed on the workpiece. The slit groove formation system aligns the center of the image data obtained by the camera with the reference mark. The nozzle is shifted on the workpiece by a distance between the nozzle and the camera which is determined in advance in order to align the nozzle with the reference mark formed on the workpiece. Following the above process, the nozzle is relatively shifted or moved on the workpiece based on the reference position. The pillar of the high-pressure water jet is then supplied or jetted onto the slit groove formation position on the workpiece.
However, the above alignment manner in the related-art method only has a positioning accuracy of ±50 μm because the position of the reference mark is determined based on the image data obtained by the camera of the slit groove formation system. Although this positioning accuracy is acceptable for a rough forming process and the like, but it is not acceptable for a fine structure forming process such as the slit groove formation process of not more than 100 μm width. In the slit groove formation process, a large amount of error between the formation position of the pillar of the high-pressure water jet corresponding to the slit groove formation position and the irradiation position of the laser light which passes through the pillar of the high-pressure water jet. This causes various problems such as the variations in width and step of the slit grooves formed in the molding die.
For the above reason, it is demanded to develop and provide a method of producing a molding die for use in producing (such as extruding and molding) honeycomb structure bodies made of ceramic material, capable of preventing the occurrence of variations in width and step of the slit grooves formed in the molding die.